Viterbi detector

Abstract

A path-select-signal memory section in the Viterbi detector outputs each decoded data B′ Si k corresponding to a branch that occurred a prescribed time ago in a surviving path to each state at a present time, in response to path select signals SEL 0 , SEL 1 . A shift register stores the path select signals SEL 0 , SEL 1 in order of time. A binary output unit outputs a decoded bit corresponding to a branch that occurred a prescribed time ago in a surviving path. Output signal lines of the binary output unit and a selector train are connected according to a trellis diagram that corresponds to encoding operation.

1. A Viterbi detector for maximum-likelihood decoding of a convolutionally-encoded input signal, comprising:
 a branch metric calculating section for calculating branch metrics from the convolutionally-encoded input signal; 
 an ACS (Add-Compare-Select) operation section for calculating a path metric for each state at a present time using both a path metric of a previous time in a surviving path of that state and a corresponding branch metric calculated by the branch metric calculating section, and outputting a path select signal corresponding to a metric selected by the ACS operation; 
 a path-select-signal memory section responsive to the path select signal, for outputting, at a present time, decoded data in a surviving path having a prescribed constraint length, wherein the data are decoded at a corresponding branch a prescribed time ago; and 
 a maximum-likelihood determination section for determining most likely decoded data from each decoded data received from the path-select-signal memory section, wherein 
 the path-select-signal memory section includes 
 a shift register for storing the path select signals in order of time, 
 a selector train formed by a plurality of selectors for receiving values stored in respective cells of the shift register as a select signal, and 
 a binary output unit for outputting a decoded bit corresponding to a branch that is decoded a prescribed time ago in the surviving path. 
 
   
   
     2. The Viterbi detector according to  claim 1 , wherein the maximum-likelihood determination section determines most likely decoded data from each of the decoded data according to majority logic, and outputs the most likely decoded data. 
   
   
     3. The Viterbi detector according to  claim 1 , wherein the maximum-likelihood determination section selects any one of the decoded data for output as most likely data. 
   
   
     4. The Viterbi detector according to  claim 1 , wherein the path-select-signal memory section includes a register train formed from a plurality of registers for pipeline processing. 
   
   
     5. The Viterbi detector according to  claim 1 , wherein the convolutionally-encoded input signal is produced from data whose shortest pulse width is limited to a value equal to or larger than two channel bits. 
   
   
     6. The Viterbi detector according to  claim 1 , wherein the convolutionally-encoded input signal is produced by equalizing data whose shortest pulse width is limited to a value equal to or larger than two channel bits by a PR (Partial Response) method. 
   
   
     7. The Viterbi detector according to  claim 1 , wherein the convolutionally-encoded input signal is produced by NRZI (Non Return to Zero Inverted)-converting an RLL (Run Length Limited) (2, 10)-encoded signal and then equalizing the resultant signal by a PR method. 
   
   
     8. The Viterbi detector according to  claim 1 , wherein the convolutionally-encoded input signal is produced by NRZI-converting an RLL (1, 7)-encoded signal and then equalizing the resultant signal by a PR method. 
   
   
     9. The Viterbi detector according to  claim 1 , wherein the Viterbi detector is used in a magnetic disk reproducing device. 
   
   
     10. The Viterbi detector according to  claim 1 , wherein the Viterbi detector is used in an optical disk reproducing device. 
   
   
     11. The Viterbi detector according to  claim 1 , wherein output signal lines of the binary output unit and the selector train are connected according to a trellis diagram that corresponds to encoding operation of the convolutionally-encoded input signal. 
   
   
     12. The Viterbi detector according to  claim 1 , wherein said plurality of selectors are directly connected to one another according to a trellis diagram.